Solar Terrestrial Activity Report

Last major update issued on May 12, 2012 at 06:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 12, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to active on May 11. Solar wind speed at SOHO ranged between 521 and 568 km/s under the influence of a high speed stream from CH515.

Solar flux measured at 20h UTC on 2.8 GHz was 136.4 (increasing 38.3 over the last solar rotation). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 14.8). Three hour interval K indices: 43322322 (planetary), 44332321 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).

Region 11475 [N06W39] reemerged with 2 tiny spots.
Region 11476 [N09W09] decayed losing penumbral area and a few spots. There was a significant reduction in both positive and negative polarity umbral area in the southern part of the huge penumbra. The region appears less complex but still has the potential to produce major flares. Flares: C6.1 at 17:38 UTC and numerous sub C5 level flares. The region was involved in a significant filament eruption that began after 18h UTC and included AR 11480 and extended eastwards.
Region 11477 [S23E35] was quiet and stable.
Region 11478 [S24E43] was quiet and stable.
New region 11479 [N14E67] rotated into view at the northeast limb on May 10 and was numbered the next day by SWPC.
New region 11480 [S17W12] emerged in the southeast quadrant on May 8 and was noticed by SWPC 3 days later. The region decayed on May 11.

Spotted active regions not numbered by NOAA/SWPC:
S1642 [S16E12] decayed slowly and quietly.
New region S1646 [N15E79] rotated into view at the northeast limb.
New region S1647 [N11E35] emerged with two spots.

Coronal mass ejections (CMEs)

May 9-10: No obviously Earth directed significant CMEs were observed in STEREO imagery.
May 11: A filament eruption began after 18h UTC and involved a large area around the center of the disk, including the southern part of AR 11476, AR 11480 and extending towards the east. A CME was observed in STEREO-B at 23:54 UTC and in STEREO-A a couple of hours later when images resumed. The CME is likely Earth directed.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A southern hemisphere coronal hole (CH516) was Earth facing on May 9-10.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair to good.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 12 and quiet to active on May 13 due to a high speed stream from CH516. The CME observed late on May 11 could reach Earth on May 14 and cause unsettled to minor storm conditions that day and on May 15.

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region	Date numbered detected	Spot count			Location at midnight	Area	Classification		SDO / HMI 4K continuum image with magnetic polarity overlay		Comment
		SWPC	STAR SDO				SWPC	STAR	Current	Previous
			2K	1K
11474	2012.05.01 2012.05.02				N16W52						plage location: N17W46
11475	2012.05.02		2	1	N05W49						location: N06W39
11476	2012.05.04 2012.05.05	47	122	54	N11W05	1040	FKC	FKC			beta-gamma-delta area: 1400 location: N09W09
S1631	2012.05.04				S24W38						plage
S1633	2012.05.06				N12W27						plage
11477	2012.05.07 2012.05.08	1	7	3	S22E31	0080	HSX	CSO			location: S23E35
11478	2012.05.08 2012.05.10	1	5	3	S24E42	0060	HSX	CSO			area: 0120
11480	2012.05.08 2012.05.11	2	2	1	S16W10	0010	AXX	HRX
S1637	2012.05.08				N23W42						plage
S1638	2012.05.08				S19W46						plage
S1639	2012.05.08				S16W57						plage
S1642	2012.05.09		4		S16E12	0000		BXO
11479	2012.05.10 2012.05.11	1	2	1	N15E65	0090	HSX	HSX			location: N14E67
S1645	2012.05.10				S12E09						plage
S1646	2012.05.11		2	2	N15E79	0100		DSO
S1647	2012.05.11		2		N11E35	0000		AXX
Total spot count:		52	148	65
Sunspot number:		102	238	135	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		77	181	98	(Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		61	83	74	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.